Lesson 6: Recycling materials/ Decomposition/ DECAY RP

Question 1

What two parts of an ecosystem do materials cycle through?

Answer 1

• Materials cycle through the abitiotic and biotic components of an ecosystem.

Question 2

Why are all materials in the living world recycled?

Answer 2

• All materials in the living world are recycled to provide the building
  blocks for future organisms.

Question 3

What happens in the carbon cycle?

Answer 3

• The carbon cycle returns carbon from organisms to the atmosphere as
  carbon dioxide to be used by plants in photosynthesis.

Question 4

What happens in the water cycle? Why is it useful?

Answer 4

• The water cycle provides fresh water for plants and animals on land
  before draining into the seas. Water is continuously evaporated and
  precipitated.

Question 5

How is the carbon in carbon dioxide used by plants and algae after they take in carbon dioxide by photosynthesis?

Answer 5

• Used to make carbohydrates, fats, proteins (other molecules.)

Question 6

What happens when animals eat plants ? (in terms of carbon.)

Answer 6

• Carbon is used by animal to make other molecules (carbohydrates, fats and proteins.)

Question 7

When animals excrete , what is in their faeces?

Answer 7

• Carbon

Question 8

When plants and animals die, what is still stored in their remains?

Answer 8

• Carbon

Question 9

What happens to an animal’s excreted faeces or remains (after it has died?)

Answer 9

• Faeces and remains are broken down by decomposing bacteria ie. bacteria and fungi.
• Decomposers release carbon dioxide (by actually decomposing)/ by them respiring.

Question 10

Why are decomposers ie. bacteria and fungi really important?

2 main reasons

Answer 10

1.) Cycle materials through ecosystem by returning carbon to the atmosphere as carbon dioxide.
2.) They release mineral ions to soil.

Question 11

What 3 things happen to fresh precipitated water?

Answer 11

• Passes through rocks.
• Evaporated back into air.
• Forms rivers/ streams.

Question 12

What happens to the water from river/ streams?

Answer 12

• It provides fresh water for plants/ animals.
• But then, drains back into the sea.

Question 13

What are the 3 conditions required for decomposition to happen?

Answer 13

1.) Warm temperature (enzymes working faster.)
2.) Good supply of water.
3.) Sufficient amount of oxygen.

Question 14

What do gardeners and farmers try to do to produce compost (from waste/ biological material?)

Answer 14

• Try to provide optimum conditions for rapid decay of waste and biological material.

Question 15

What is compost (produced by gardeners and farmers) used for?

Answer 15

• The compost produced is used as a
  natural fertiliser for growing garden plants or crops.

Question 16

What is a product of anaerobic decay?

Answer 16

• Methane gas

Question 17

What machine/ device can be used to produce methane gas as a fuel?

Answer 17

• Biogas generators can be
  used to produce methane gas as a fuel.

Question 18

What is the method for investigating decay of milk at different temperatures, required practical?

10 MAIN steps

Answer 18

1.) Label a test-tube “lipase”
2.) Use pipette to place 5cm3 of lipase into test tube.
3.) Label another test-tube “milk” and add few drops of indicator: **Cresol Red. **
4.) Add 5cm3 of milk/ 7cm3 of sodium carbonate solution to this test-tube. Solution should be purple.
5.) Place thermometer in milk test-tube.
6.) Place both test-tubes into a beaker of water (water = specific temp.)
7.) Wait until temp of solutions is same as water in beaker.
8.) Use a pipette to 1cm3 transfer lipase solution to test-tube containing milk/ start a timer.
9.) Once solution of milk turns yellow, stop timing.
10.) Repeat experiment at different temperatures of water in the beaker.

Question 19

What colour is Cresol Red in alkaline conditions?

Answer 19

• Cresol Red is “purple” in alkaline conditions.

Question 20

Why is the milk solution (at the beginning, before lipase is added) purple?

Answer 20

• Sodium carbonate is alkaline.
• Cresol Red is purple in alkaline conditions.

Question 21

What is the control variable in the decay of milk required practical?

Answer 21

• Volumes of ALL the solutions

Question 22

What are important things that you must do in this practical?

Answer 22

• Use clean test-tube for milk solution (to make sure there are no traces of lipase left.)
• Subjective when to stop the timer. Calculate a MEAN time.

Question 23

Why does the solution of milk turn yellow once you leave lipase in there for a while?

Answer 23

• Lipase breaks down milk into fatty acids.
• Cresol red turns yellow in acidic conditions.

Question 24

Why do we use LIPASE in the milk, instead of allowing the milk solution to decay naturally?

Answer 24

• Decay is a very slow process.
• So, we use lipase to model it.